On-demand ejection for injection molds

ABSTRACT

An injection-molding machine includes various devices for increasing production efficiency and protecting the mold from closing on molded articles. A method for increasing production efficiency and protecting the mold from closing on articles, or portions thereof, is disclosed. This detection system and method determines if a molded article, or portion thereof, remains in the mold after the first ejection sequence has occurred. This condition is determined by the article-detection controller which enables the molding machine controller to perform the next molding cycle if the said molded article, or portion thereof, is not detected in said mold. The article-detection controller enables the molding machine controller to perform an additional ejection sequence on the mold ejector system if said molded article, or portion thereof, is detected in said mold. If the molded article, or portion thereof, is detected in said mold after the second ejection, subsequent ejection sequences and inspections are performed to self-correct the problem. After exhausting the predetermined number of ejection sequences, the molding machine controller will signal for alternative intervention.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable.

FEDERALLY SPONSORED RESEARCH

Not Applicable.

SEQUENCE LISTING OR PROGRAM

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention relates to a system and method for increasing productionefficiency and protecting injection molds.

2. Prior Art

Articles molded in an injection mold may not eject from the mold's firstejection sequence. The inherent characteristics of the material beingmolded, the geometry of the article, or molding imperfections, such asflash, often cause an unsuccessful first ejection sequence. Portions ofmolded articles may remain in the mold after the first ejection sequencedue to a failure in the ejection system, breakage of the molded article,or insufficient material being supplied to the mold cavity. If themolded articles, or portions thereof, are not properly ejected from themold prior to the mold closing, mold damage can occur or subsequentmolded articles may be defective. If multiple ejection sequences areperformed to ensure that articles, or portions thereof, have ejectedprior to mold closing, production efficiency is compromised.

Article-sensing vision systems and radiation emitting and receivingarticle sensors are currently utilized to protect injection molds, butthese devices simply prevent the mold from initiating its next cycle andtypically require operator intervention to correct the problem. If thetime for the operator to react to the identified problem is significant,the material in the machine's barrel can degrade, requiring additionaltime and expense for the material to be purged. Molding machines areoften equipped with a low-pressure mold protection feature, closing themold at a lower pressure in an attempt to detect any resistance at moldclosing due to an unwanted article in the mold. Low-pressure moldprotection does not protect the mold when the low pressure is enough todamage the mold, or when improper ejection occurs often. To help reducethe potential for mold damage and reduce operator intervention, it iscommon to increase the amount of ejection sequences during the moldingcycle, decreasing production efficiency. Increasing productionefficiency, protecting the mold, increasing part quality, and reducingoperator requirements are important since these directly relate to thecost of the molded articles and the competitiveness of the molder.

3. Objects and Advantages

Accordingly, several objects and advantages of my invention are:

-   (a) an increase in production efficiency by adding ejection    sequences on demand-   (b) protection of the mold from closing on molded articles, or    portions thereof-   (c) better quality by ensuring molded articles, or portions thereof,    are properly ejected, not compromising the integrity of subsequent    molded articles-   (d) a reduction in operator intervention.

Further objects and advantages of my invention will become apparent froma consideration of the drawings and ensuing description.

SUMMARY

This invention provides a method of performing ejection sequences in aninjection mold on demand, increasing production efficiency andprotecting the mold.

DRAWINGS

FIG. 1 is a perspective view of a mold equipped with article-detectiondevices

FIG. 2 is a section view of the mold illustrating an improperly ejectedarticle

FIG. 3 is a section view of a through-beam radiation emitting andreceiving article sensor

FIG. 4 is a section view of a reflective radiation emitting andreceiving article sensor

DRAWING REFERENCE NUMERALS

-   10 Ejector-half of injection mold-   12 Hot-half of injection mold-   14 Article-sensing vision system-   16 Through-beam radiation receiving sensor-   18 Through-beam radiation emitting sensor-   20 Reflective radiation emitting and receiving sensor-   22 Mold ejector system-   24 Article-detection controller-   26 Molding machine controller-   28 Connecting device-   30 Molded article, or portion of an article-   32 Radiation beam.

DETAILED DESCRIPTION

FIGS. 1 and 2 depict systems for detecting the presence of an article,or portion of an article 30, in the mold after the ejection sequence ofthe injection molding cycle has occurred.

FIG. 1 illustrates an article-sensing vision system 14 mounted to thehot-half of the mold 12 and a through-beam radiation receiving sensor16, a through-beam radiation emitting sensor 18, and a reflectiveradiation emitting and receiving sensor 20 attached to the ejector-halfof the mold 10. Article-detection devices are not limited toarticle-sensing vision systems 14, and radiation emitting and receivingsensors 16,18,20. The simultaneous use of multiple article-sensingsystems such as an article-sensing vision system 14 and radiationemitting and receiving article sensors 16,18,20 as depicted in FIG. 1 isnot required. The article-sensing vision system 14 and radiationemitting and receiving article sensors 16,18,20 are electricallyconnected to the article-detection controller 24. The article-detectioncontroller 24 is connected to the molding machine controller 26. Theconnecting device 28 between the article-sensing devices 14,16,18,20,the article-detection controller 24, and the molding machine controller26 could be any connecting device known to the ordinarily skilledartisan such as, and not limited to, electrical cords, wiring, cables,or fiber optic cables.

FIG. 2 illustrates an article, or a portion thereof 30, in the moldafter the ejection sequence of the injection-molding cycle has occurred.FIG. 3 illustrates how an article, or portion thereof 30, not properlyejected from the mold would be detected by through-beam radiationreceiving and emitting sensors 16,18. The improperly ejected article, orportion thereof 30, interferes with the radiation beam 32 emitted fromthe through-beam radiation emitting sensor 18, preventing thethrough-beam radiation receiving sensor 16 from detecting the radiationbeam 32. FIG. 4 illustrates how an article, or portion thereof 30, notproperly ejected from the mold would be detected by a reflectiveradiation emitting and receiving sensor 20. The radiation emitters andreceivers 16,18,20 could be any device known to the ordinarily skilledartisan and could be, and not limited to, infrared light sources, whitelight sources, light emitting diodes, photoresistors, photodiodes,phototransistors, or photovoltaic cells. These devices also includeappropriate lenses to increase detecting distances and modify thedetection area.

Operation—FIG. 1 and FIG. 2

When the article-detection devices, such as the article-sensing visionsystem 14 or radiation emitting and receiving article sensors 16,18,20,detect a molded article, or portion of an article 30, thearticle-detection controller 24 is alerted of the condition. Thearticle-detection controller 24 enables the molding machine controller26 to perform an additional ejection sequence on the mold ejector system22. The mold ejector system 22 can encompass all methods of ejectionknown to the ordinarily skilled artisan such as, and not limited to,mechanical ejection and pneumatic ejection. If the molded article, orportion thereof 30, is not detected by the article-detection devicesafter the second ejection, the mold is allowed to close and start itsnext cycle. If the molded article, or portion thereof 30, is detected bythe article-detection devices after the second ejection, subsequentejection sequences and inspections are performed to self-correct theproblem. After exhausting the predetermined number of ejectionsequences, the molding machine controller 26 will signal for alternativeintervention.

From the description above, a number of advantages of the system becomeevident:

-   a) An increase in production efficiency will be realized since only    the required amount of ejection sequences will be utilized in any    molding cycle, eliminating the need to have a conservative amount of    ejection sequences on every cycle-   b) The mold has increased protection from damage caused by closing    on an improperly ejected article, or portion of an article, that    remains in the mold-   c) Better quality by ensuring molded articles, or portions thereof,    are properly ejected, not compromising the integrity of subsequent    molded articles-   d) A reduction in operator intervention will be realized since the    system will attempt to self-correct improperly ejected articles, or    portions thereof, before signaling for alternative intervention.

These advantages enable a higher production efficiency, lower laborcost, and better preservation of the mold than with existing methods.

Although the description above contains many specifics, these should notbe construed as limiting the scope of the invention, but as merelyproviding illustrations of some of the presently preferred embodimentsof this invention. For example, the article-detection controller andmolding machine controller can be one and the same, wirelesscommunications can be utilized to communicate between the devices, etc.The scope of the invention should be determined by the appended claimsand their legal equivalents, rather than by the examples given.

1. A method of performing additional ejection sequences in an injectionmold on demand comprising the steps of: a) Detecting the presence of amolded article, or portion thereof, in the injection mold b) Initiatingthe next molding cycle if the said molded article, or portion thereof,is not detected in the said mold c) Activating an ejection sequence ifsaid molded article, or portion thereof, is detected in said mold
 2. Themethod of detecting the presence of said molded article, or portionthereof, of claim 1 is accomplished with a vision-system
 3. The methodof detecting the presence of said molded article, or portion thereof, ofclaim 1 is accomplished with one or more radiation emitting andreceiving sensors
 4. The method of detecting the presence of said moldedarticle, or portion thereof, of claim 1 detects the presence of saidmolded article, or portion thereof, in said injection mold and portionsof the mold which are not in position prior to initiating said nextcycle
 5. Said article, or portion thereof, of claim 1 is the molded part6. Said article, or portion thereof, of claim 1 is a byproduct ofmolding the part
 7. Said ejection sequences of claim 1 are mechanicalsequences
 8. Said ejection sequences of claim 1 are pneumatic sequences9. Said injection mold of claim 1 is a plastic-injection mold
 10. Saidinjection mold of claim 1 is a metal-injection mold
 11. Said injectionmold of claim 1 is a silicon-injection mold
 12. Said molded article, orportion thereof, of claim 1 is a plastic-injection molded article, orportion thereof
 13. Said molded article, or portion thereof, of claim 1is a metal-injection molded article, or portion thereof
 14. Said moldedarticle, or portion thereof, of claim 1 is a silicon-injection moldedarticle, or portion thereof